Collapsible-expandable prosthetic heart valves with structures for clamping native tissue

ABSTRACT

A prosthetic heart valve is designed to be circumferentially collapsible for less invasive delivery into the patient. At the implant site the valve re-expands to a larger circumferential size, i.e., the size that it has for operation as a replacement for one of the patient&#39;s native heart valves. The valve includes structures that, at the implant site, extend radially outwardly to engage tissue structures above and below the native heart valve annulus. These radially outwardly extending structures clamp the native tissue between them and thereby help to anchor the prosthetic valve at the desired location in the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/688,357, filed Apr. 16, 2015, which is a continuation of U.S. patentapplication Ser. No. 11/906,133, filed Sep. 28, 2007, now U.S. Pat. No.9,532,868, the disclosures of which are hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

This invention relates to prosthetic heart valves, and more particularlyto prosthetic heart valves that can be collapsed to a relatively smallsize for delivery into a patient and then re-expanded to full operatingsize at the final implant site in the patient.

At present there is considerable interest in prosthetic heart valvesthat can be collapsed to a relatively small circumferential (or annularperimeter) size for delivery into a patient (e.g., through tubulardelivery apparatus like a catheter, a trocar, laparoscopicinstrumentation, or the like). This is of interest because it can helpto make replacement of a patient's defective heart valve less invasivefor the patient. When the prosthetic valve reaches the desired implantsite in the patient, the valve is re-expanded to a largercircumferential (or annular perimeter) size, which is the full operatingsize of the valve.

Because of the interest in prosthetic heart valves of the above generaltype, improvements to valves of this type are always being sought.

BRIEF SUMMARY OF THE INVENTION

In accordance with certain possible aspects of the invention, aprosthetic heart valve may include an annular structure that isannularly continuous and that has an annular perimeter that ischangeable in length between (1) a first relatively small lengthsuitable for delivery of the valve into a patient with reducedinvasiveness, and (2) a second relatively large length suitable for useof the annular structure to engage tissue of the patient adjacent to thepatient's native valve annulus and thereby implant the valve in thepatient. The valve further includes a flexible leaflet structureattached to the annular structure. The annular structure may comprise anannular array of diamond-shaped cells. Upstream apex portions of atleast some of these cells may be resiliently biased to deflect radiallyoutwardly from at least some other portions of the annular structure,and downstream apex portions of at least some of these cells may also beresiliently biased to deflect radially outwardly from at least someother portions of the annular structure. As a result, when the valve isin use in a patient, tissue of the patient adjacent to the patient'snative heart valve annulus is clamped between the upstream anddownstream apex portions, with the upstream apex portions engagingtissue upstream from the annulus, and with the downstream apex portionsengaging tissue downstream from the annulus.

In accordance with certain other possible aspects of the invention, aprosthetic aortic heart valve may include an annular structure that isannularly continuous and that has an annular perimeter that ischangeable in length between (1) a first relatively small lengthsuitable for delivery of the valve into a patient with reducedinvasiveness, and (2) a second relatively large length suitable for useof the annular structure to engage tissue of the patient adjacent to thepatient's native aortic valve annulus and also downstream from ostia ofthe patient's coronary arteries to thereby implant the valve in thepatient. The annular structure may include an annularly continuousannulus portion adapted for implanting adjacent the patient's nativeaortic valve annulus upstream from the ostia of the patient's coronaryarteries, and an annularly continuous aortic portion adapted forimplanting in the patient's aorta downstream from those ostia. Theannulus portion and the aortic portion are preferably connected to oneanother only by a plurality of linking structures that are disposed topass through at least a portion of the patient's valsalva sinus atlocations that are spaced from the ostia of the patient's coronaryarteries in a direction that extends annularly around the valsalvasinus. The valve further includes a leaflet structure that is attachedto the annulus portion. The annulus portion includes first and secondtissue clamping structures that are spaced from one another along anaxis that passes longitudinally through the valve, each of the clampingstructures being resiliently biased to extend radially outwardly fromthe leaflet structure, whereby, in use, tissue of the patient adjacentto the patient's native aortic valve annulus is clamped between thefirst and second clamping structures, with the first clamping structureengaging tissue upstream from the annulus, and with the second clampingstructure engaging tissue downstream from the annulus.

In accordance with certain still other possible aspects of theinvention, a prosthetic aortic heart valve includes an annular structurethat is annularly continuous and that has an annular perimeter that ischangeable in length between (1) a first relatively small lengthsuitable for delivery of the valve into a patient with reducedinvasiveness, and (2) a second relatively large length suitable for useof the annular structure to engage tissue of the patient adjacent to thepatient's native aortic valve annulus and thereby implant the valve inthe patient. The valve further includes a flexible leaflet structureattached to the annular structure. When a valve having these aspects ofthe invention is implanted in the patient, any non-leaflet part of thevalve that is at the level of the patient's native coronary artery ostiais confined in a direction that is circumferential of the valve to areasthat are adjacent to the patient's native aortic valve commissures ordownstream projections of those commissures, each of said areas havingan extent in the circumferential direction that is less than thedistance in the circumferential direction between circumferentiallyadjacent ones of those areas. In addition, the annular structureincludes first and second tissue clamping structures that are spacedfrom one another along an axis that passes longitudinally through thevalve. Each of the clamping structures is resiliently biased to extendradially outwardly from the leaflet structure, whereby, in use, tissueof the patient adjacent to the patient's native aortic valve annulus isclamped between the first and second clamping structures, with the firstclamping structure engaging tissue upstream from the annulus, and withthe second clamping structure engaging tissue downstream from theannulus.

Further features of the invention, its nature and various advantages,will be more apparent from the accompanying drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of some components of an illustrativeprosthetic valve in accordance with the invention.

FIG. 2 is a simplified schematic diagram of a representative portion ofapparatus like that shown in FIG. 1 in relation to some native tissuestructures of a patient in accordance with the invention.

FIG. 3 is generally similar to FIG. 2 for some other native tissuestructures of a patient.

FIG. 4 is a simplified elevational view of another illustrativeembodiment of apparatus in accordance with the invention. FIG. 4 showsthe depicted apparatus in its collapsed/pre-expanded state, and asthough cut along a vertical line and then laid out flat.

FIG. 5 is generally similar to FIG. 4 for another illustrativeembodiment in accordance with the invention.

FIG. 6 is a simplified elevational view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 7 is a simplified perspective view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 8 is a simplified perspective view showing an illustrativeembodiment of another component added to what is shown in FIG. 7 inaccordance with the invention.

FIG. 9 is generally similar to FIG. 8 , but shows an alternativeembodiment with additional possible features in accordance with theinvention.

FIG. 10 is generally similar to FIG. 9 , but shows an illustrativeembodiment of more components added to what is shown in FIG. 9 inaccordance with the invention.

FIG. 11 is a simplified perspective view showing in more detail arepresentative portion of the components that are added in FIG. 10 .

FIG. 12 is a simplified perspective view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 13 is a simplified perspective view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 14 is a simplified elevational view of still another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 15 is generally similar to FIG. 14 , but shows an illustrativeembodiment of more components added to what is shown in FIG. 14 inaccordance with the invention.

FIG. 16 is a simplified elevational view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 17 is a simplified elevational view of another illustrativeembodiment of apparatus in accordance with the invention.

FIG. 18 is a simplified elevational view of another illustrativeembodiment of a prosthetic heart valve in accordance with the invention.

FIG. 19 is a simplified perspective view of an embodiment like thatshown in FIG. 18 with other possible elements added in accordance withthe invention.

FIG. 20 is a simplified elevational view of another illustrative of aprosthetic heart valve in accordance with the invention.

FIG. 21 is a simplified perspective view of another illustrativeembodiment of a component for a prosthetic heart valve in accordancewith the invention.

FIG. 22 is a simplified perspective view of another illustrativeembodiment of a prosthetic heart valve in accordance with the invention.

FIG. 23 is a simplified perspective view of another illustrativeembodiment of a prosthetic heart valve in accordance with the invention.

FIG. 24 is a simplified perspective view of another illustrativeembodiment of a component for a prosthetic heart valve in accordancewith the invention.

FIG. 25 is generally similar to FIG. 24 for still another illustrativeembodiment of a component for a prosthetic heart valve in accordancewith the invention.

FIG. 26 is a simplified elevational view of yet another illustrativeembodiment of a component for a prosthetic heart valve in accordancewith the invention.

FIG. 27 is a simplified perspective view of still another illustrativeembodiment of a prosthetic heart valve in accordance with the invention.

FIG. 28 is a simplified cross section of a typical patient tissuestructure that is useful for explaining certain principles of theinvention.

DETAILED DESCRIPTION

Certain components of an illustrative embodiment of a prosthetic heartvalve 10 in accordance with the invention are shown in FIG. 1 . Valve 10is designed for use as a replacement for a patient's native aorticvalve. (Other valve types will be considered later in thisspecification.) FIG. 1 shows valve 10 in its expanded condition, i.e.,the condition that the valve has when implanted in the patient. Thedepiction of valve 10 that is provided in FIG. 1 may omit certaincomponents that the valve may have, but to some extent this is done tobetter reveal the components that are depicted in FIG. 1 . Moreinformation will be provided about these possibly omitted componentslater in this specification. Also, FIG. 1 shows by representative arrows42 and 44 that certain parts of the structure shown in the FIG. maydeflect farther out and down (in the case of the parts associated witharrows 42) or farther out and up (in the case of the parts associatedwith arrows 44) than happens to be shown in FIG. 1 . This will also beexplained in more detail later in this specification.

Among the components of valve 10 are an annular metal structure20/30/40, and a leaflet structure 100. Metal structure 20/30/40 forms acomplete, continuous annulus around a longitudinal axis (not shown) thatpasses through the center of the valve. This central longitudinal axisis vertical, given the orientation of the valve shown in FIG. 1 .Structure 20/30/40 can be reduced in annular size from the size shown inFIG. 1 by compressing that structure in the annular or circumferentialdirection. When this is done, structure 20/30/40 shrinks by partialcollapse of the diamond-shaped cells 22 and 46 of aortic portion 20 andannulus portion 40. Later FIGS. will show examples of how such cellsand/or other collapsible shapes can collapse or shrink in a directionthat is annular of the valve. In other words, when the structure is thusmade to shrink in the annular direction, the length of the perimetermeasured around the outside of the valve becomes smaller. There is nosignificant change in the overall topological shape of the valve,especially metal structure 20/30/40, between its large and smallperimeter sizes or at any time as it transitions between those sizes.For example, if the valve is approximately a circular annulus in itsfull (FIG. 1 ) size, it remains an approximately circular annulus as itis reduced to its smaller perimeter size. It is preferred that there beno folding, wrapping, overlapping, or other major topological shapechange of metal structure 20/30/40 to reduce its perimeter size or tosubsequently re-expand it.

The above-described changes (i.e., collapsing and re-expanding) of metalstructure 20/30/40 are preferably all elastic deformations. For example,metal structure 20/30/40 can be resiliently biased to have the size andshape shown in FIG. 1 . In such a case, collapsing of metal structure20/30/40 to the above-mentioned smaller perimeter, annular, orcircumferential size can be by elastic deformation of the metalstructure, e.g., by confining metal structure 20/30/40 in a tube havinga smaller perimeter than the full FIG. 1 size of the valve. Such a tubecan be part of apparatus for delivering the valve into a patient. Whenthe valve is pushed or pulled out of the tube, metal structure 20/30/40automatically, elastically, re-expands to the full size shown in FIG. 1. Because such a delivery tube can be smaller than the full size of thevalve, the valve can be delivered into the patient less invasively thanwould be possible if the valve was only capable of always remaining fullsize as shown in FIG. 1 .

As an alternative or addition to full elastic compression andself-re-expansion, re-expansion may be at least partly assisted by othermeans. For example, an inflatable balloon on a catheter may be used toassist valve 10 to re-expand to its full size. Such a balloon may betemporarily positioned inside valve 10 to accomplish this. This may bedone either because the elastic re-expansion is not quite strong enoughto get the valve back to full size when adjacent to surrounding nativetissue of the patient, because some plastic re-expansion is required toget the valve back to full size, to help ensure that the valve does infact firmly seat in and engage the desired surrounding native tissue atthe implant site, or for any other reason. For the most part it will beassumed herein that all or substantially all compression andre-expansion are elastic, but the possibility of some plasticcompression and re-expansion is also contemplated as mentioned earlierin this paragraph.

We turn now to a description of the various parts of metal structure20/30/40. Part 20 is intended for implantation in the patient's nativeaorta downstream from the native aortic valve location, and alsodownstream from the patient's native valsalva sinus. Part 20 maytherefore be referred to as the aortic portion of the valve or of metalsupport structure 20/30/40. Portion 20 is a completely annular(continuous) structure, with the ability to annularly collapse andre-expand as described earlier in this specification. Portion 20 is madeup principally of an annular array of parallelogram- or diamond-shapedcells 22, which give portion 20 the ability to annularly compress andre-expand as described.

Part 40 is intended for implantation in the patient's native aorticvalve annulus. Part 40 may therefore be referred to as the annulusportion of the valve or of metal support structure 20/30/40. Part 40 isalso a completely annular (continuous) structure, with the ability toannularly collapse and re-expand as described earlier in thisspecification. Part 40 is again made up primarily of an annular array ofparallelogram- or diamond-shaped cells 46, which give portion 40 theability to annularly compress and re-expand as described.

Part 40 also includes three commissure post members 50 that are spacedfrom one another (e.g., approximately equally) around the valve. Eachcommissure post member 50 is intended for implantation at theapproximate angular or circumferential location of a respective one ofthe patient's native aortic valve commissures. Like the nativecommissures, posts 50 are structures at which adjacent ones of the threeleaflets of structure 100 came together in pairs. The blood inflow edgeportions (lower as viewed in FIG. 1 ) of each leaflet are also securedto other structure of the valve below posts 50. The blood outflow edgeportions of leaflets 100 (upper as viewed in FIG. 1 ) are free (exceptfor their end attachments to a respective pair of posts 50). These freeedges can come together to close the valve when blood pressuredownstream from the valve is greater than blood pressure upstream fromthe valve. When the blood pressure differential reverses, the greaterupstream blood pressure pushes the free edges of the leaflets apart,thereby opening the valve to allow blood flow through it.

Leaflet structure 100 is typically made of three flexible leafletsheets. The material of these sheets can be any known flexible leafletmaterial such as appropriately treated natural tissue, a flexiblepolymer, or the like.

Each of commissure posts 50 is preferably at least partly cantileveredup (in the blood flow direction) from remaining structure of part 40.For example, toward its blood inflow (lower) end, each of posts 50 maybe attached to other structure of part 40 only near and/or below themiddle of that part in the longitudinal (vertical) direction. At leastthe upper (blood outflow) end portion of each post 50 is thereforecantilevered from that post's lower-end-portion connections to otherstructure of part 40. The upper end portion of each post 50 isaccordingly preferably a free end (i.e., without any metal connection toother adjacent metal structure of part 40). This has a number ofadvantages. One of these advantages is that it makes at least the upperportions of posts 50 at least somewhat independent of the other metalstructure 20/30/40 of the device. This makes it possible for at leastthe upper portions of posts 50 to have properties like flexurecharacteristics, deflection characteristics, final locationcharacteristics, etc., that can be optimized for the purposes that thesepost portions must serve, while other portions of metal structure20/30/40 can be relatively independently optimized in these variousrespects for the various purposes that these other portions of structure20/30/40 must serve. As an example of this, it may be desirable for theupper portions of posts 50 to stand relatively straight up and to haveflexibility that is optimized for absorbing stress from the lateraledges of the leaflets 100 that are attached to those posts. At the sametime, it may be desirable for other portions of metal structure 20/30/40that are at the same general level along the longitudinal axis of thevalve to flare radially out to various degrees. This will be describedin more detail later in this specification. But just to complete thepoint that has been started here, it may be desired for the upperportions of cells 46 to be strong enough to hold back native leafletsand/or native leaflet remnants, and/or to deflect down onto the bloodoutflow surface of the native valve annulus (especially in cases inwhich the native leaflets have been wholly or largely removed).Similarly, it may be desirable for the members of strut structures 30 tobegin to incline radially outwardly as they extend towardcircumferentially larger aortic portion 20 and/or as they pass throughthe patient's native valsalva sinus, which is also circumferentiallylarger than the native valve annulus.

Clarification of a point of terminology may be appropriate here. Whenthis specification speaks of a structure extending radially outwardly orthe like, this does not necessarily mean that this structure is exactlyperpendicular to a longitudinal axis extending in the blood flowdirection through the valve. It may only mean that the structure has atleast some component of alignment that is radial of the valve, i.e.,that the structure (or a geometric projection of the structure) formssome angle with the above-mentioned longitudinal axis. In short, as ageneral matter, a “radially extending structure” or the like does nothave to be fully or exactly radial of the above-mentioned longitudinalaxis, but may instead have only some vector component that is radial ofthat axis.

The aortic portion 20 and the annulus portion 40 of metal structure20/30/40 are connected to one another by what may be termed struts orstrut structures 30. In the illustrative embodiment shown in FIG. 1there are six of these struts 30. They are in three pairs, with eachpair being adjacent to a respective one of the three commissure posts50. More particularly, the two struts 30 in each pair are preferablylocated adjacent (and relatively close to) respective opposite sides ofthe associated post 50. This arrangement leaves relatively large openareas (in the circumferential direction) between the pairs of struts 30.In other words, the distance in the circumferential direction betweenthe struts 30 in any pair of those struts is preferably less than thecircumferential distance between the two circumferentially closeststruts in any two different pairs of those struts. Because commissureposts 50 are angularly or rotationally aligned with the patient's nativeaortic valve commissures, and because struts 30 pass through thepatient's native valsalva sinus relatively close to longitudinalprojections of posts 50, struts 30 are thus located to pass through thevalsalva sinus (typically close to or at the wall of the valsalva sinus)along paths that are circumferentially spaced from the ostia of thepatient's coronary arteries. In other words, struts 30 are preferablylocated in the circumferential direction to pass through the valsalvasinus without any possibility of a strut obstructing the ostium of acoronary artery. (Although patient anatomy can vary in this respect, thecoronary artery ostia are typically located in the valsalva sinusbetween the native aortic valve commissures (or between longitudinalprojections of the native aortic valve commissures). See also the laterdiscussion of FIG. 28 , which discussion applies to embodiments of thekind generally illustrated by FIG. 1 . In particular, in the terms laterdiscussed in connection with FIG. 28 , all material of structure 30 atthe level of the coronary artery ostia should be confined to areas W asshown in FIG. 28 .)

In addition to the characteristics that are mentioned above, each ofstruts 30 is preferably serpentine in the longitudinal direction (i.e.,as one proceeds along the length of any strut 30 from annulus portion 40to aortic portion 20, the strut deviates from a straight line, first toone side of the straight line, then to the other side of the straightline, then back to the first side, and so on). One of the benefits ofthis type of strut configuration is that it can increase the lateralflexibility of structure 20/30/40, especially the lateral flexibility ofstrut portion 30 between portions 20 and 40. Lateral flexibility meansflexibility transverse to a longitudinal axis that is parallel to bloodflow through the valve. Prior to and during implantation, this lateralflexibility can help the valve more easily follow curves ininstrumentation that is used to deliver the valve into the patient.After implantation, this lateral flexibility can help each of portions20 and 40 seat more concentrically in its respective portion of thepatient's anatomy, which portions may not be exactly perpendicularlyconcentric with one single, common, central longitudinal axis.

As shown in FIG. 1 , the upper end of each strut 30 may connect to thelower end (or apex) of one of the cells 22 of aortic portion 20. Thelower end of each strut 30 may similarly connect to the upper end (orapex) of one of the cells 46 of annulus portion 40. It should be noted,however, that especially at the lower end of strut structure 30 thereare other cells 46 of annulus portion 40 that have no struts 30connected to their upper ends or apexes. For example, arrows 42 areshown adjacent to the upper ends of two representative ones of cells 46of this kind. These are the cells 46 whose upper portions can beconfigured to deflect or project radially outwardly (as indicated by thearrows 42) for such purposes (mentioned earlier, and also in more detaillater) as holding back any remaining native leaflet material and/orclamping down on the blood outflow side of the patient's native valveannulus.

From the foregoing, it will be seen that the features of valve 10 forholding the valve in place in the patient can include any or all of thefollowing: (1) the radially outward projection of some or all of thelower portions of annulus cells 46 adjacent the blood inflow side of thenative aortic valve annulus; (2) the radially outward projection of theupper portions of at least some of the upper portions of annulus cells46 adjacent possibly remaining native aortic leaflet tissue and/oradjacent the blood outflow side of the native aortic valve annulus; (3)the general radial outward expansion of annulus portion 40 against thenative valve annulus; (4) the radial outward expansion of aortic portion20 to annularly engage the inner wall surface of the aorta downstreamfrom the valsalva sinus; and (5) the possible engagement of the innerwall surface of the valsalva sinus by strut structures 30 passingthrough that sinus. Although not shown in FIG. 1 , it is possible to addto any suitable portion(s) of metal structure 20/30/40 barbs thatproject out from other adjacent structure so that they additionallyengage, dig into, and/or penetrate tissue to give the implanted valveadditional means for maintaining its position in the patient.

Note also that in addition to possibly engaging possibly remainingnative aortic valve leaflet tissue, valve 10 has many structures forpushing any such remaining tissue radially outwardly away from possibleinterference with prosthetic leaflet structure 100. These structuresinclude the upper portions of all of cells 46 and the lower portions ofall of struts 30.

There are some other possible features of valve 10 that have not yetbeen mentioned. One of these aspects is the provision of apertures like52 through commissure posts 50 (and possibly other portions of metalstructure 20/30/40) for facilitating the attachment (e.g., using suturematerial or other similar strand material) of leaflet structure 100 tothe metal structure. Other layers of material such as tissue, fabric, orthe like may also be attached to various parts of metal structure20/30/40 for various purposes. These purposes may include (1) helping toprevent, reduce, or cushion contact between leaflet structure 100 andmetal structure 20/30/40; (2) helping to improve sealing between thevalve and the surrounding native tissue (e.g., to prevent paravalvularleakage); and (3) helping to promote tissue in-growth into the implantedvalve. Limited examples of such additional layers of material are shownin FIG. 1 in the form of lower fabric skirt 110 and blood inflow edgesealing ring 120. Both of structures 110 and 120 extend annularly aroundthe outside of the lower (blood inflow) edge of valve 10. Structureslike 110 and 120 may be held to metal structure 20/30/40 by sutures orother similar strand-like material, and apertures (like 52) through themetal structure (or other features of the metal structure) may be usedto provide anchoring sites for such sutures or the like. Still otherpossible aspects of valve 10 will be discussed in connection with laterFIGS.

A possibly important feature of valves in accordance with the presentinvention is that they can include a structure near the blood inflowedge for clamping adjacent native tissues in a particular way. Inparticular, the upper and lower portions of at least some of cells 46can both pivot toward one another from a common central location. Thisis illustrated schematically in FIGS. 2 and 3 .

FIG. 2 shows the somewhat simpler case in which the patient's nativeaortic valve leaflets have been removed prior to implanting valve 10.The native tissue structures that are visible in FIG. 2 are a portion220 of the wall of the left ventricle, a portion 210 of the aortic valveannulus, and a portion 230 of the wall of the valsalva sinus. The upperportion of a representative cell 46 from FIG. 1 is shown schematicallyin FIG. 2 by member 142. The lower portion of that cell is shownschematically by member 144. Members 142 and 144 can pivot toward oneanother about central pivot point 143. As in FIG. 1 , this is againindicated by arcing arrows 42 and 44. Thus members 142 and 144 initiallyform a relative large, open jaw structure, the two jaws of which can bereleased to resiliently pivot toward one another to clamp down on anytissue within their reach. In the case of FIG. 2 , this can include someof the tissue of sinus wall 230 and the upper surface of annulus 210(for upper pivoting member 142), and some of the tissue of leftventricle wall 220 and the lower surface of annulus 210 (for lowerpivoting jaw member 144). Clamping force vector component diagrams inFIG. 2 indicate the nature of the clamping forces that can result fromthese kinds of tissue engagement. For example, member 142 can have aradially outward clamping force component 142 a and a longitudinallydownward clamping force component 142 b. Similarly, member 144 can havea radially outward clamping force component 144 a and a longitudinallyupward clamping force component 144 b. Opposing clamping forcecomponents 142 b and 144 b tend to clamp tissue between members 142 and144. But radially outward force components 142 a and 144 a also engagetissue and therefore also help to hold valve 10 in place in the patient.

FIG. 3 illustrates the somewhat more elaborate case in which nativeaortic leaflet tissue 240 (typically, or at least often, stenotic)remains in the vicinity of prosthetic valve 10 when the valve isimplanted. FIG. 3 shows that in this type of situation upper member 142both engages leaflet tissue 240 and helps to push it radially out of theway. Again, member 142 exerts both a radially outward force component142 a and a longitudinal (downward) force component 142 b on theadjacent tissue (in this case leaflet tissue 240). The behavior andeffects of lower member 144 are similar to what is shown in FIG. 2 anddescribed earlier. Thus again the structures of valve 10 exert bothradial outward tissue engaging forces 142 a/144 a and oppositelydirected tissue clamping forces 142 b/144 b to hold valve 10 in place inthe patient.

Recapitulating and extending the above, the attachment method of thepresent design applies forces in the radial and longitudinal directionsto clamp onto several anatomical features, not just annulus 210. Indoing this, a valve in accordance with this invention can maximize (orat least significantly increase) the orifice area at the annulus levelfor better blood flow. Another way of thinking about the present designsis not necessarily as “clamps,” but rather as members of a stent thatconforms to the different diameters of different portions of theanatomy. Structures that only “clamp” tend to engage only both sides ofthe native annulus (like 210), and do not also extend to and engageother tissue structures as in the present designs. The presentstructures also differ from “clamp” structures that terminate from asingle pointed wire. Instead, in the present designs, the conformingmembers are formed from continuous strut members of the base (annulusportion 40) of the stent. This can only be achieved with an annulusportion 40 that stays below the ostia of the coronary arteries and withcommissure posts 50 that are “independent” of other structure of annulusportion 40 as was described earlier in this specification.

Still other features of the present valves that warrant emphasis arementioned in the following. The annulus portion 40 of the present valvespreferably expands as nearly as possible to the full size of the nativevalve annulus. The leaflet structure 100 is preferably mounted justinside annulus portion 40. This helps the present valves avoid anystenotic character (such as would result from having the leafletstructure or some other structure on which the leaflet structure ismounted) spaced radially inwardly from annulus portion 40. The presentvalves are thus ensured to have the largest opening for blood to flowthrough, which reduces the pressure gradient (drop) across the valve.

Note that at the level of the coronary artery ostia, the present valveshave only very minimal non-leaflet structure 30; and even that minimalnon-leaflet structure is rotationally positioned to pass through thevalsalva sinus where it will safely bypass the coronary artery ostia.Annulus portion 40 is preferably designed to be entirely upstream (inthe blood flow direction) from the coronary artery ostia. Aortic portion20, on the other hand, is preferably designed to be entirely downstreamfrom the coronary artery ostia (i.e., in the aorta downstream from thevalsalva sinus). Some prior designs have much more extensive non-leafletstructures extending much farther into or through the valsalva sinus andtherefore longitudinally beyond the coronary artery ostia. This isbelieved to be less desirable than the present structures.

The present valves preferably include “independent” commissure posts 50that are “lined up” or aligned with (i.e., superimposed over) the nativevalve commissures. This also helps to ensure proper coronary arteryflow, when combined with the fact that struts 30 are confined to beingclosely adjacent to posts 50 in the circumferential direction. Evenrelatively thin connecting members (like struts 30) could partiallyblock a coronary artery if not correctly positioned in thecircumferential direction around the valsalva sinus. But this is avoidedin the present valves by the principles and features mentioned, forexample, in the immediately preceding sentences.

FIG. 4 shows another illustrative embodiment of metal support structure20/30/40. FIG. 4 shows this structure as though cut along its length andthen laid flat. FIG. 4 also shows this structure in the condition thatit has in its circumferentially collapsed condition. Thus, for example,the sides of what will be diamond-shaped cells 22 and 46 in there-expanded valve are, in FIG. 4 , collapsed down to being parallel withone another. Again, the fact that FIGS. like FIG. 4 show structures asthough cut longitudinally and laid flat is only for ease and convenienceof depiction. In actual fact these structures are complete andcontinuous annular structures like the structure 20/30/40 shown in FIG.1 .

Note that in the FIG. 4 design there are eyelets 24 in aortic section 20for attachment of material and/or attachment of wires/sutures for adelivery system. On annulus section 40 the eyelets 48/52 can be used forattachment of the cuff, porcine buffer, and/or leaflets. FIG. 4 shows anannulus portion 40 with a “scalloped” inflow (lower) edge. Thisscalloped blood inflow edge is relatively “high” in the vicinity of theinflow end of each commissure post 50, and relatively “low” betweencommissure post 50 inflow ends. (“High” means more downstream; “low”means more upstream.) This can help the implanted valve avoid affectingthe patient's mitral valve, which tends to be radially spaced from theaortic valve along a radius of the aortic valve that corresponds to theradial location of one of the aortic valve's commissures. Because thevalves of this invention are preferably implanted with posts 50superimposed inside the native valve commissures, this places one of the“high” portions 41 of the inflow edge adjacent the patient's mitralvalve. The resulting recessing 41 of annulus portion 40 helps theprosthetic valve avoid interfering with the mitral valve.

FIG. 5 shows yet another illustrative embodiment of metal supportstructure 20/30/40. FIG. 5 shows this embodiment in the same general wayand condition as FIG. 4 shows its embodiment. Thus, as said inconnection with FIG. 4 , the structure shown in FIG. 5 is actually acomplete, continuous annulus, and the longitudinally cut and flatteneddepiction shown in FIG. 5 is only employed for simplicity and greaterclarity.

The FIG. 5 embodiment again has eyelets 24 in the aortic section 20 forattachment of material and/or attachment of wires/sutures for a deliverysystem. Also, eyelets 48/52 on annulus section 40 can be used forattachment of the cuff, porcine buffer, and/or leaflets. As compared tothe FIG. 4 design (in which connecting support struts 30 are connectedto the downstream apexes of certain annulus portion cells 46), in FIG. 5the connecting support struts 30 are connected directly to posts 50. Theaortic portion 20 of the FIG. 5 embodiment also has two annular arraysof cells 22 a and 22 b (rather than only one annular array of such cells22 as in the earlier embodiments). Array 22 a is more downstream thanarray 22 b, but these two arrays do overlap somewhat in the longitudinaldirection by virtue of the cells in the two arrays having someintervening cell members (like representative member 23) in common.

A typical way of making any of the support structures 20/30/40 of thisinvention is to laser-cut them from a tube.

FIG. 6 shows another illustrative embodiment of aortic portion 20, inwhich the cells 22 of the mesh stent can expand against the ascendingaorta. This structure may or may not be covered in tissue, polymer,and/or fabric (true for any of the embodiments shown and describedherein).

FIGS. 7 and 8 show another illustrative embodiment of annulus portion40. This mesh stent has expandable cells that press against the nativevalve annulus and/or leaflets (if the native leaflets remain). Upper 142and lower 144 portions of this stent clamp down on the native annulusand/or leaflets. This stent design is symmetrical around thecircumference, but it may be asymmetrical to allow anatomicalconformance with the mitral valve, for example. A cuff 110 made offabric, tissue, or polymer may fully or partially encapsulate this stentas shown, for example in FIG. 8 .

FIGS. 9 and 10 show an embodiment of stent 40 that includes a set ofbarbs 43 on the top and/or bottom to further secure the stent in orderto stop migration. A partial cuff 110 (FIG. 10 ) allows the barbed tips43 to be exposed to direct tissue contact for enhanced securing. Thebottom section could be asymmetrical (e.g., as in FIGS. 4 and 5 ) tomitigate any impingement on the mitral valve. An extra-thick, toroidalsection 112 of the cuff allows extra sealing capacity to preventparavalvular leakage.

FIG. 11 shows that toroidal section 112 of cuff 110 allows extra sealingcapacity to prevent paravalvular leakage. This section could be made ofextra fabric, tissue, or polymer. The chamber 114 inside section 112 canaccommodate an injectable polymeric substance to aid in seating.

FIG. 12 shows another illustrative embodiment of the aortic holdingportion 20. In this case portion 20 is a metallic or polymericexpandable wire form with many of the same attributes discussed with themesh stent.

FIG. 13 shows another illustrative embodiment of annulus/leaflet holdingportion 40. In this case portion 40 is a metallic or polymericexpandable wire form with many of the same attributes discussed with themesh stent.

FIGS. 14 and 15 show an illustrative assembly of an aortic portion 20and an annulus portion 40. In FIG. 15 a pliable or semi-rigid reinforcedfabric 30 connects the aortic portion 20 and the annulus/cuff portion40/110/112 to allow somewhat independent movement. The tissue orsynthetic leaflets 100 can then be attached to connecting section 30.All of the disclosed variations allow for ample areas (like 130) forblood to flow to the coronaries.

The variation shown in FIG. 16 does not include an aortic portion 20.Instead, three independent commissure posts 50 allow for leafletattachment (e.g., with the aid of apertures 52), while the base 40 issecured in place as described earlier. Posts 50 can be lined up with thenative commissures and (by virtue of the recesses like the oneidentified by reference number 41) allow for an opening on the lowerportion to be clear of chordae and the mitral valve. The posts 50 usedto attach the leaflets may be solid or have any combination of holes,slots, and/or other apertures 52.

Note that even for an embodiment like FIG. 16 , when used for an aorticvalve, any non-leaflet portion of the valve (such as commissure posts50) that extends into the coronary sinus to the level of any coronaryartery ostium is confined, in the circumferential direction, tolocations that are well spaced from the coronary artery ostia. This ispreferably accomplished by having all such non-leaflet structureconfined (in the circumferential direction) to locations or areas thatare at or circumferentially near the native aortic valve commissures (ordownstream projections of those commissures). The circumferential widthof each of these areas in which non-leaflet structure is permitted atthe level of the coronary artery ostia is preferably less than thecircumferential spacing at that level between circumferentially adjacentones of those areas. It is not a problem for moving leaflet material toextend to or even beyond the level of the coronary artery ostia becausethe coronary arteries can fill with blood when the valve is closed. Butno non-leaflet and therefore basically non-moving part of the prostheticvalve should be allowed to occupy any location at the level of thecoronary artery ostia where that non-leaflet material may interfere withblood flow into the coronary arteries.

FIG. 28 illustrates the point made in the immediately precedingparagraph (and also elsewhere in this specification). FIG. 28 shows across section of a typical patient's valsalva sinus 300 at the level ofthe coronary artery ostia. The patient's native aortic commissures (ordownstream projections of those commissures) are at locations 310 a-c.The coronary artery ostia typically occur in bracketed areas 320. Anynon-leaflet structure of a prosthetic valve in accordance with thisinvention that is at the level depicted by FIG. 28 should be confined toareas W. The width of each of these areas in the circumferentialdirection (i.e., the dimension W) is preferably less than the distance Sin the circumferential direction between any two circumferentiallyadjacent ones of these areas.

FIG. 17 shows another illustrative embodiment that is somewhat like theembodiments in FIGS. 1, 4, and 5 in that there is a continuous link 30between aortic section 20 and annulus section 40. In this embodimentlink structure 30 itself allows for leaflet attachment, with the lowerportion of each link 30 acting like a commissure post 50. To mitigateleaflet abrasion at the attachment site in this or any other embodiment,the stent may first be covered with fabric, followed by a thin layer ofbuffering tissue/polymer, and finally the leaflet tissue/polymer. Thestent of the valve can be partially or completely covered in one or acombination of materials (polyester, tissue, etc.) to allow for betterin-growth, abrasion protection, sealing, and protection from metalleachables like nickel from nitinol.

Most of the detailed discussion thus far in this specification hasrelated to prosthetic aortic valves. However, certain aspects of whathas already been said can also be applied to making prosthetic valvesfor other locations in the heart. The mitral valve is another valve thatfrequently needs replacement, and so this discussion will now turn topossible constructions for other valves such as the mitral valve.

In the case of the mitral valve (which supplies blood from the leftatrium to the left ventricle), only the native valve annulus area(possibly including what is left of the native valve leaflets) isavailable for anchoring the prosthetic valve in place. There is nothingcomparable to the aorta for additional downstream anchoring of aprosthetic mitral valve.

Structures of the types shown in FIGS. 7-11 and 13 are suitable for usein prosthetic mitral valves. In such use, annular structure 40 may bedelivered into the native mitral valve annulus in a circumferentiallycollapsed condition and then re-expanded to the depicted size andcondition in that annulus. The apex portions 142 of cells 46 at one endof structure 40 (e.g., the blood inflow end) project resiliently out andalso pivot somewhat downstream as shown, for example, in FIG. 7 andengage the patient's tissue adjacent the inflow side of the patient'snative mitral valve annulus. Apex portions 144 of cells 46 at the otherend of structure 40 (e.g., the blood outflow end) project resilientlyout and also pivot somewhat upstream and engage the patient's tissueadjacent the outflow side of the patient's native valve annulus. Thetissue of and adjacent to the mitral valve annulus is thereby clampedbetween tissue clamping structures 142 and 144. Barbs 43 may be added asshown in FIGS. 9 and 10 for additional tissue engagement and possiblepenetration to additionally help hold the valve in place in the mitralvalve annulus. Other features (e.g., 110 and 120) and principlesdiscussed earlier in connection with FIGS. 7-11 and 13 apply to thepossible mitral valve use of these structures and features.

An illustrative embodiment of a more fully developed prosthetic mitralvalve 210 in accordance with the invention is shown in FIG. 18 . In thisdepiction of mitral valve 210, its blood inflow end is down, and itsblood outflow end is up. (This depiction may be regarded as “upsidedown” as compared to its orientation in a patient who is standingupright.) Analogous to what is shown in FIG. 16 , valve 210 has threecommissure posts 50 that are cantilevered from annular structure 40.Flexible valve leaflets 100 are attached to these posts (and elsewhereto other structure of the valve such as annular structure 40 and/ormaterial that is used to cover structure 40). Apertures 52 through posts50 may be used to facilitate attachment (e.g., suturing) of the leafletsto the posts. Additional apertures 54 in posts 50 may be used as sitesfor or to facilitate attachment of chordae tendonae (native and/orartificial replacements) to the posts. This last point will beconsidered further as the discussion proceeds.

The posts 50 used to attach the leaflets can be solid or can have anycombination of holes and/or slots. Three independent posts 50 (i.e.,“independent” because cantilevered from annular structure 40) allow forleaflet attachment, while the base 40 is secured in place as describedearlier. Also, posts 50 can be lined up with the native anatomy forbetter leaflet opening clear of chordae and the aortic valve. Apertures54 can be included near the downstream free ends of posts 50 for nativeand/or artificial chordae attachment. To mitigate leaflet abrasion atthe attachment site, the stent 40 can first be covered with fabric,followed by a thin layer of buffering tissue/polymer, and finally theleaflet 100 tissue/polymer. As is true for all embodiments herein, thestent 40 of the valve can be partially or completely covered in one or acombination of materials (polyester, tissue, etc.) to allow for betterin-growth, abrasion protection, sealing, and protection from metalleachables such as nickel from nitinol. The support structure 50 for theleaflets may be continuous from the clamping stent portion 40.Alternatively, the leaflet support structure may be a separate sectionconnected to clamping portion 40, or it may be frameless.

FIG. 19 shows an example of how artificial and/or native chordae 220 canbe attached prior to, during, or after implanting prosthetic mitralvalve 210. These chordae attachments are made at or near the downstreamfree ends of posts 50. Chordae 220 can be adjusted through coredpapillary muscles and/or through a port made in the apex of the beatingheart.

FIG. 20 shows an alternative embodiment of prosthetic mitral valve 210in which chordae 230 can be attached to an extended free edge 102 of theleaflets prior to, during, or after implanting of the valve in thepatient. Once again, chordae 230 can be adjusted through cored papillarymuscles and/or through a port made in the apex of the beating heart. Theredundant coaptation portions 102 of the leaflets can be reinforcedtissue (e.g., a double layer or thicker tissue), or if the leaflet is apolymer, it can be reinforced by greater thickness and/or fibers.

FIG. 21 shows that the stent 40 design can include apertures 48 aroundthe center portion of the stent to allow for cuff, leaflet, and chordaeattachment around the circumference of the stent. FIG. 22 shows that theedge of cuff 110 can follow the edge shape of stent 40 to allow forpassage of chordae and reduction of interference of other anatomy, whilealso allowing greater flexibility of annular structure 40. FIG. 23 showschordae 240 extending from apertures like those shown at 48 in FIG. 21 .

FIG. 24 illustrates the point that variations in stent cell 46 geometryaround the circumference of annular structure 40 can reduce impingementon or of the aortic valve, chordae, and the coronary sinus.Additionally, extended portions (e.g., 244) of some cells may allow forgreater holding force in certain parts of the anatomy such as in theatrial appendage.

FIGS. 25 and 26 show other variations in the shape of annular structure40 that can allow for better conformance to the mitral valve anatomy.For example, FIG. 25 shows an asymmetric shape, while FIG. 26 shows asymmetric saddle shape.

FIG. 27 shows that a valve 210 with an elliptical shape may also conformbetter to the mitral valve anatomy than a circular-shaped valve.Additionally, instead of a tri-leaflet design, FIG. 27 shows that abi-leaflet design 100′ can be used (leaflets shown open in FIG. 27 ).Once again, chordae 220 can be attached at commissure posts 50, and theedge of cuff 110 can be contoured to follow the edge of stent 40.

Although the structures shown in FIGS. 18-27 are described primarily asmitral valve structures, it will be understood that this is onlyillustrative, and that various structures and principles illustrated byor in these FIGS. can be employed in other types of prosthetic heartvalves (e.g., in prosthetic aortic valves).

Briefly recapitulating some of what has been said in somewhat differentterms, it will be seen that in many embodiments of the invention, atleast the portion 40 of the prosthetic valve that goes in the patient'snative valve annulus includes an annular array of generallydiamond-shaped cells 46. Upstream apex portions 144 of at least some ofthese cells are resiliently biased to deflect radially outwardly from atleast some other portions of structure 40. Downstream apex portions 142of at least some of these cells are similarly resiliently biased todeflect radially outwardly from at least some other portions ofstructure 40. This allows the valve to clamp tissue of the patientbetween the upstream and downstream apex portions that thus deflectoutwardly.

Each of the above-mentioned apex portions comprises two spaced-apartmembers that join at an apex of that apex portion. For example, in FIG.7 the two spaced-apart members of one representative downstream apexportion are identified by reference letters b and c, and the apex wherethose members join is identified by reference letter a.

Still more particularly, the resiliently biased, radially outwarddeflection of each upstream apex portion 144 typically includes adownstream component of motion of that upstream apex portion (inaddition to a radially outward component of motion). This isillustrated, for example, by the arcuate arrows 44 in FIGS. 1-3 .Similarly, the resiliently biased, radially outward deflection of eachof downstream apex portion 142 typically includes an upstream componentof motion of that downstream apex portion (in addition to a radiallyoutward component of motion). This is illustrated, for example, by thearcuate arrows 42 in FIGS. 1-3 . The result of this is that the upstreamand downstream apex portions begin as jaws that are relatively far apartand wide open. They then effectively pivot toward one another to clamptissue therebetween.

References herein to an annular perimeter of a structure beingchangeable in length mean that the perimeter increases or decreases insize without going through any major topological change. In other words,the shape of the structure remains basically the same, and only theperimeter size changes. For example, the shape may be always basicallycircular. There is no folding or wrapping of the structure to change itsperimeter size. The shape either basically shrinks down or expands out.A minor exception to the foregoing is that ellipses and circles areregarded herein as having the same basic topology. Thus an ellipse mayshrink to a circle, for example, without that constituting “a majortopological change.”

It will be understood that the foregoing is only illustrative of theprinciples of the invention, and that various modifications can be madeby those skilled in the art without departing from the scope and spiritof the invention. For example, the particular patterns of stent cellslike 22 and 46 shown herein are only illustrative, and many other stentconfigurations can be used instead if desired. It will be appreciatedthat the valves of this invention can, if desired, be implanted in apatient less invasively. For example, the valves of this invention canbe implanted percutaneously, trans-apically, or surgically, and with orwithout resected and/or debrided leaflets. Depending on the embodiment,the valve can be collapsed in a variety of configurations beforedeployment in a single- or multi-stage process. Access can be achieved,for example, through the femoral artery, abdominal aorta, or the apex ofthe heart.

The invention claimed is:
 1. A prosthetic heart valve, comprising: astent having an inflow end, an outflow end, an expanded condition and acollapsed condition, the stent including an annularly continuous annulusportion adjacent the inflow end and a plurality of commissure posts eachhaving a connected end connected to the annulus portion and a free end,the annulus portion including a plurality of closed perimeterdiamond-shaped cells, each cell having an upstream apex portion directlyconnected to a downstream apex portion at connection points, theupstream apex portion having an upstream apex and the downstream apexportion having a downstream apex, the stent being devoid of structurebetween adjacent ones of the commissure posts from the connected ends tothe free ends, the upstream apex portion of each cell in a group of thecells being resiliently biased to deflect radially outwardly from theconnection points and the downstream apex portion of each cell in thegroup of the cells being resiliently biased to deflect radiallyoutwardly from the connection points; an expandable and collapsiblevalve element mounted within the stent; and a skirt connected to theannulus portion of the stent.
 2. The prosthetic heart valve as claimedin claim 1, wherein the skirt extends annularly around the annulusportion and has a first annular edge positioned downstream from theupstream apices and a second annular edge positioned upstream from thedownstream apices.
 3. The prosthetic heart valve as claimed in claim 2,wherein each upstream apex in a group of the upstream apices includes abarb and each downstream apex in a group of the downstream apicesincludes a barb.
 4. The prosthetic heart valve as claimed in claim 2,further comprising a barb on each of the upstream apices and on each ofthe downstream apices.
 5. The prosthetic heart valve as claimed in claim1, wherein the skirt includes a chamber disposed in a circumferentialdirection around the annulus portion of the stent.
 6. The prostheticheart valve as claimed in claim 5, wherein the chamber is filled with apolymeric substance.
 7. The prosthetic heart valve as claimed in claim1, wherein the skirt has an inflow end, an outflow end, and a length ina longitudinal direction of the stent that is less than a length of theannulus portion so that the skirt outflow end is positioned upstreamfrom the downstream apices of the annulus portion.
 8. The prostheticheart valve as claimed in claim 1, wherein the skirt covers the annulusportion of the stent from the upstream apices to the downstream apices.9. The prosthetic heart valve as claimed in claim 1, wherein the skirtincludes an inner wall disposed in a circumferential direction aroundthe annulus portion of the stent, and a closed toroidal section disposedin the circumferential direction around the inner wall.
 10. Theprosthetic heart valve as claimed in claim 9, wherein the inner wall ofthe skirt has a first length in the longitudinal direction of the stentand the toroidal section has a second length in the longitudinaldirection of the stent, the second length being less than the firstlength.
 11. The prosthetic heart valve as claimed in claim 1, whereineach of the commissure posts includes an aperture at the free end.
 12. Aprosthetic heart valve, comprising: a stent having an inflow end, anoutflow end, an expanded condition and a collapsed condition, the stentincluding an annularly continuous annulus portion adjacent the inflowend, an annularly continuous aortic portion adjacent the outflow end,and a plurality of commissure posts each having a first end connected tothe annulus portion and a second end connected to the aortic portion,the annulus portion including a plurality of closed perimeterdiamond-shaped cells, each cell having an upstream apex portion directlyconnected to a downstream apex portion at connection points, theupstream apex portion having an upstream apex and the downstream apexportion having a downstream apex, the stent being devoid of structurebetween adjacent ones of the commissure posts from the first ends to thesecond ends, the upstream apex portion of each cell in a group of thecells being resiliently biased to deflect radially outwardly from theconnection points and the downstream apex portion of each cell in thegroup of the cells being resiliently biased to defect radially outwardlyfrom the connection points; an expandable and collapsible valve elementmounted within the stent; and a skirt connected to the annulus portionof the stent.
 13. The prosthetic heart valve as claimed in claim 12,wherein the skirt extends annularly around the annulus portion and has afirst annular edge positioned downstream from the upstream apices and asecond annular edge positioned upstream from the downstream apices. 14.The prosthetic heart valve as claimed in claim 13, further comprising abarb on each of the upstream apices and on each of the downstreamapices.
 15. The prosthetic heart valve as claimed in claim 12, whereinthe skirt includes an inner wall disposed in a circumferential directionaround the annulus portion of the stent, and a closed toroidal sectiondisposed in the circumferential direction around the inner wall.
 16. Theprosthetic heart valve as claimed in claim 15, wherein the inner wall ofthe skirt has a first length in the longitudinal direction of the stentand the toroidal section has a second length in the longitudinaldirection of the stent, the second length being less than the firstlength.
 17. The prosthetic heart valve as claimed in claim 15, whereinthe inner wall has a first annular edge positioned downstream from theupstream apices and a second annular edge positioned upstream from thedownstream apices.